PHILADELPHIA (CBS) — City officials say safety is the number one concern for tomorrow’s Fourth of July “Wawa Welcome America” festivities, along the Benjamin Franklin Parkway.

Everett Gillison, deputy mayor for public safety, is asking folks to come prepared:

“The one thing that I can tell you that we’ve been watching, and watching closely, from a public safety point of view, is the weather. It is hot. You’ve got to wear light clothing. Keep hydrated. We will have EMS (emergency medical services) out here. We will have everyone ready to do what’s necessary to keep you safe, but we want you to play your part.”

As far as security is concerned, deputy police commissioner Kevin Bethel is asking attendees to bring clear carrying bags if possible, and leave the coolers at home.

He says that with about 500,000 people expected along the Parkway, this is their largest police deployment yet for the “Welcome America” celebration.

“You’re gonna see a lot of the stuff we did last year,” Bethel says. “We’re just gonna enhance it a little bit: some different dynamics. We haven’t dealt with a Friday night in quite a while, so we’re anticipating what that will do to the crowd because there’s no workday the next day.”

And he says they’ve improved their security plan to try to prevent an incident like last year in which someone threw a firecracker into the crowd.

“What we are trying to do, to the best of our ability, is to make sure we have our men and women deployed strategically enough that if we see an event like that unfold, we can intercept it, get in there very quickly, neutralize that push and flow and protect those individuals as much as possible.”